Such diaphragms are standard components in diaphragm valves for use in process and systems technology for conveying any media in a pipeline. The functional principle of a diaphragm is in general always based on providing an elastically deformable wall, with the aid of which the flow cross section may be modified in the area of the valve seat. For this purpose, the elastic diaphragm is moved in the direction of the valve seat or away from the valve seat.
DE 20 2014 103 142 U1 discloses a diaphragm valve having a diaphragm including the features of the preamble from Claim 1. Furthermore, the reinforcing fabric layering in the interior of the carrier material of the membrane is introduced. Further membranes featuring a reinforcement layer completely embedded in the elastomer are disclosed in DE 2 063 509, DE 74 20 903, DE 102 26 410 and U.S. Pat. No. 2,615,471. Membranes featuring a reinforcement layer on the side of the elastomer facing towards the media are disclosed in U.S. Pat. No. 3,130,954. DE 20 2009 013 401 discloses a diaphragm being circulated on both sides in an overrun air recirculation valve. U.S. Pat. No. 6,230,609 discloses multilayered elastomer diaphragms.
These requirements for such a diaphragm heavily depend on the installation situation and the field of application of the diaphragm valve. Conventionally, the diaphragm in a diaphragm valve is pressed under preloading force into a resting position. The background is that, in the case of a power and/or pressure failure, it is imperative to know the switching position of the valve. If the valve now is to be switched, an actuator, which overcomes the preloading force and forces the diaphragm into an alternative switching position, is actuated. This conventionally is carried out with the aid of pressurized air, solenoid coils or the like. The switching process is carried out in sudden bursts and, depending on the specific application, is carried out repeatedly or once only.
Against this background, the diaphragm of a diaphragm valve has to fulfill two different criteria: On the one hand, it has to be ensured that the diaphragm in the closed position of the diaphragm valve sufficiently seals. This is carried out in that the elastic base body of the diaphragm is compressed against the valve seat and, in so doing, a sealing surface is generated. Thus, the diaphragm has to be sufficiently elastic. Furthermore, the elasticity of the diaphragm has to be so high that the fast switching processes do not result in component failure.
On the other hand, the diaphragm has to withstand constant compression stresses, in particular for diaphragm valves which are closed in their resting position. It has to be ensured that plastic deformations and/or tears do not result in the diaphragm. Thus, the base body furthermore has to have a certain capability of resistance. Moreover, in the closed state, the total pressure of the medium to be retained is always applied at the diaphragm. The diaphragm has to withstand this counter pressure, without which a formation of tears or a deformation of the diaphragm results. In general, the challenge of optimization is now to improve the elasticity and the capability of resistance of the diaphragm. Conventional diaphragms having elastomers as a base body achieve the required elasticity for generating the sealing effect; however, they often do not achieve the required capability of resistance in regard to the formation of tears.
In order to address this optimization issue, the prior art suggests that the elastomer of the diaphragm features a reinforcement layer, which is configured in the interior of the elastomer. In this instance, the reinforcement layer is to provide the necessary tear strength of the diaphragm, and the elastomer is to provide the elasticity of the diaphragm. Thus, it results that such reinforced diaphragms, which are known from the prior art, substantially have three layers.
Since the mentioned reinforcement layer completely runs in the interior of the elastomer, the outer effective surfaces of the diaphragm and the total thickness of the diaphragm remain unaltered, as a result of which design changes in the valve body are not required.
For the purpose of simplification, it can be assumed that a defined thickness of the elastomer is technically predefined. This thickness is selected so that the diaphragm is sufficiently flexible and adequately resistant when interacting with the reinforcement layer. If now a reinforcement layer is configured within the diaphragm, the thickness of the elastomer remains constant in sum; however, the reinforcement layer insert reduces, typically halves, the thickness of the elastomer, which forms between the outside of the elastomer and the reinforcement layer.
This entails various disadvantageous effects. For example, it may be disadvantageous that the reduced thickness of the elastomer results in a sealing effect of the valve which is more prone to defects.
A further disadvantageous effect is based on the fact that the reinforcement layers are conventionally connected to the elastomer using an adhesive agent. Presently known adhesive agents however mostly include chemical components, which are not to come into contact with critical media, for example, food substances or medicaments. Moreover, a plurality of other chemical and biological processes under no circumstances are to come into contact with chemical components from the adhesive agent. As described above, a reduction of the thickness of the elastomer as a result increases, owing to the reduced wall strength of the elastomer layer adjoining the medium, the risk that the chemical components from the adhesive agent diffuse through the elastomer into the medium or that the chemical components come into direct contact with the medium because of material defects.
In conclusion, it is to be noted that reinforced diaphragms known previously have a greater strength because of the reinforcement layer; however, this entails a limited performance and a significant expenditure in manufacturing. In particular, this is based on the three-layer configuration of the diaphragm.